1. 1 Atoms and Stars IST 2420 Class 12, November 24 Fall 2008 Instructor: David Bowen Course web site: www.is.wayne.edu/drbowen/aasf08

2. 11/24/08Atoms and Stars, Class 122 2 Agenda Assignments, passbacks, initial signin sheet The semester is ending Upcoming assignments Essay 2 Reading: Chemistry Waves and the Uncertainty Principle Lab 7: Specific gravity

3. 11/24/08Atoms and Stars, Class 123 3 Upcoming … Don’t put off Essay 1!!! See me instead. This week (November 24): oReader: Chemistry oManual: Lab 7: Specific Gravity oTurn in Lab 9 as a whole Next week (December 1:) oEssay 2 due via Blackboard oLab 11 – The Orbiting Bottle oSET

4. 11/24/08Atoms and Stars, Class 124 4 Upcoming … December 8 (last regular class) oReview for Final Exam oDue: all work to count in regular grade Work can be turned in later (up to one year after the end of this semester – this course only) but will count for a Change of Grade after the regular grades are turned in. See the Syllabus for this. December 15: nothing that night but the Final Exam

5. 11/24/08Atoms and Stars, Class 125 5 Grade What-If Grade What-If (on course web site – see first slide for this URL) oReminder: to get current course average, do NOT put anything in for assignments you haven’t been graded for yet If you put anything in, remove it using “delete” key oTo see what happens if you miss assignments, put in zeroes for those (this is what I will do)

6. 11/24/08Atoms and Stars, Class 126 6 Semester is Ending! If you have been relying on being able to turn work in late, it is time to get going oAlternatives: D, F, I, drop – see counselor! Getting ready for Final: oRead Information Sheet carefully – a lot of information there oLook at Final Topics carefully oUse Review Session!

7. 11/24/08Atoms and Stars, Class 127 7 Essay 2 (Review) TOPIC: What has this course been about? You should answer this question with a core concept or idea, perhaps with dependent parts, and illustrated by referring to course experiences, such as labs and discussions, and materials, such as readings, notes, lab materials, and so on. A starting point is the “Course Description” section in the Syllabus. You can agree with, make changes to, or disagree with this description, but if you disagree, include an equivalent description – that is, one that covers the course as a whole.

8. 11/24/08Atoms and Stars, Class 128 8 Essay 2 (cont’d) This topic does NOT ask for a simple listing of all of the topics and activities (“laundry list”), and does not ask for an evaluation of me or the course (that’s for SET). The topic asks for “a” core concept and suggests a starting point for your analysis Due 12/1. At the end of tonight’s class, we will have covered all of the core topics. Review Syllabus for other requirements oAll quotes must have references

9. 11/24/08Atoms and Stars, Class 129 9 Effects of Newton’s Laws Changed view completely from planets locked on spheres with earth fixed at center (Aristotle) to bodies mutually acting on each other through known laws, with nothing fixed Each (Copernicus to Newton) saw themselves as making marginal changes to improve model supported by religion

10. 11/24/08Atoms and Stars, Class 1210Atoms and Stars, Class 1210 Newton’s Laws (cont’d) However, looking back from where we are, Newton made it possible to see a universe without a God (except for setting up universe and starting it off) oNewton: “clockwork universe,” God as clockmaker oRole of God in celestial motion is possible but not required – maybe “hand of God” as cause oWe cannot escape this change (explanation)

11. 11/24/08Atoms and Stars, Class 1211Atoms and Stars, Class 1211 What Can We Trust as a Fact? As practical matters, Newton Laws, Special Relativity, General Relativity and Quantum Mechanics (all 20 th Century) are extremely accurate, within their range of authority. Philosophically, each of the more recent ones undermines the earlier ones, even within their range of authority oPractical changes are too small to detect

12. 11/24/08Atoms and Stars, Class 1212Atoms and Stars, Class 1212 Fact? (cont’d) So science offers practical certainty, but not philosophic certainty oAlso, scientific knowledge changes Does religion offer certainty? oEach claims to be certain, but they disagree oEach claims to be eternal and unchanging, but they have changed My conclusion: humans cannot have universal, eternal truth, but we can do well enough for any practical purpose

13. The Development of Chemistry

14. 11/24/08Atoms and Stars, Class 1214 Readings – Galileo and Later

15. 11/24/08Atoms and Stars, Class 1215Atoms and Stars, Class 1215 Readings – Chemistry (Q10c#2, d) Chemistry developed after Newton (who started physics) from: oAlchemy – transmutation of elements oMedicine oIndustry – much demand for chemicals 1700s oMechanical approach from Descartes & Newton 1700 still the four Aristotelian elements oEarth – fixed volume & shape oWater – fixed volume only

16. 11/24/08Atoms and Stars, Class 1216Atoms and Stars, Class 1216 Chemistry 1700 still Aristotelian elements oAir – volume & shape expanded to container oFire - passed through container walls 1727 – Stephen Hale: released “fixed” air (put out flames) from solids, much interest 1749 Jean-Jacques DeMairan evaporated liquids (e.g. ether) in a vacuum, froze water oBut liquids supposed to evaporate into air oFire combined with liquid = air? Many types? Water could be solid, liquid, vapor –differ by fire?

17. 11/24/08Atoms and Stars, Class 1217Atoms and Stars, Class 1217 Chemistry How could “big four” be elements? 1750s Joseph Black experiments with “magnesia alba,” gave off “fixed air” that extinguished flame (CO 2 ), denser than “common air,” turned limewater cloudy oUse limewater test to show fixed air came from fermentation & charcoal combustion, would not support life “Fixed air” became specific name for this gas (CO 2 )

18. 11/24/08Atoms and Stars, Class 1218Atoms and Stars, Class 1218 Chemistry 1766 Henry Cavendish: “inflammable air” H 1772 Joseph Priestley obtained “fixed air” in other ways, demonstrated solubility in water (& taste – birth of carbonated beverage industry) oMany other types of air – “dephlogisticated air” O Phlogiston theory of combustion – burning releases phlogiston – from Germany, industrially useful –Phlogiston theory before Caloric and Kinetic theories of heat When air is saturated with phlogiston, combustion and life cease

19. 11/24/08Atoms and Stars, Class 1219Atoms and Stars, Class 1219 Chemistry Antoine Lavoisier (1743 – 1794) oGraduated in law but continued science studies oAccurate weighing, also many practical results o(Calcination – turn a metal to powder (“calx”) by heating in air below melting point – phlogiston theory explained this as driving off phlogiston) oBut Lavoisier’s weighing showed that weight of calx increased, for all metals – a problem for phlogiston theory of combustion

20. 11/24/08Atoms and Stars, Class 1220Atoms and Stars, Class 1220 Chemistry Calx of mercury (oxide of mercury) when heated gave off air (gas) that supported combustion and life oPriestley found this air better (5×) for combustion and life than “common air” (air) – “eminently respirable air” Lavoisier had assumed it was common air oLavoisier confirmed this, but common air was then a mixture

21. 11/24/08Atoms and Stars, Class 1221Atoms and Stars, Class 1221 Chemistry 1778 Lavoisier showed this air also formed acids, named it oxygen (“acid former”) (but we now know that hydrogen makes acid) 1783 Cavendish’s assistant told Lavoisier about Cavendish’s experiment of applying spark to inflammable air (H), finding dew which was identified as water oLavoisier – water was not an element, combination with oxygen for all combustion

22. 11/24/08Atoms and Stars, Class 1222Atoms and Stars, Class 1222 Chemistry Lavoisier named flammable air “hydrogen” for “water former” Lavoisier and others formed new chemical terminology – speaking well was like reasoning well oOxide – combination with oxygen oNames indicated amount of oxygen (ous < ic) Sulfurous acid H 2 SO 3 Sulfuric acid H 2 SO 4

23. 11/24/08Atoms and Stars, Class 1223Atoms and Stars, Class 1223 Chemistry Lavoisier terminology oGas – any vapor oAir – the atmosphere, a mixture (80% N, 20% O) oFire was caloric (no correct theory until 19 th century – started by Count Rumford) John Dalton (1766 – 1844), meteorologist oConverted to chemistry when he understood air was a mixture – why didn’t different gases separate by gravity?

24. 11/24/08Atoms and Stars, Class 1224Atoms and Stars, Class 1224 Chemistry John Dalton (1766 – 1844), meteorologist oAlso gases dissolved in water proportional to pressure – why? oHypothesized gases composed of atoms, each gas interacted with itself (see later slide) o“Law of definite proportions” – chemicals combined by weight in simple ratios oDalton proposed formulae based on these – chemical atomism

25. 11/24/08Atoms and Stars, Class 1225Atoms and Stars, Class 1225 Chemistry John Dalton (1766 – 1844), meteorologist oDalton proposed formulae based on these oMany of his formulae were wrong Example: he said water is HO More were right, enough to straighten out the errors over time o(DB) Physicists did not accept chemical atomism until they accepted Maxwell and Boltzmann at the end of 19 th century o(DB) Direct observations of atoms in 20 th century

26. 11/24/08Atoms and Stars, Class 1226Atoms and Stars, Class 1226 Chemistry (DB) John Dalton (1766 – 1844), meteorologist oWhat led Dalton to hypothesize atoms? Characteristics of matter –Solids cannot occupy the same space –Some liquids can –All gases can Why didn’t lighter gas rise, heavier sink? –Composition of atmosphere the same to 15,000 feet –Fog Gases could interpenetrate if it was atoms with lots of empty space in between Water could be gas, liquid, solid, these forms must have atoms Extended to all liquids and solids

27. 11/24/08Atoms and Stars, Class 1227Atoms and Stars, Class 1227 Experiment IV (not done) (Q11) Chemical composition of water Electrical current decomposes water: H 2 O  2H + O Lab Manual Pg 13

28. 11/24/08Atoms and Stars, Class 1228Atoms and Stars, Class 1228 Atomic Nature of Matter (Review) First direct evidence 1827 Robert Brown (10c#2) oNoticed spores jiggling under microscope o“Brownian motion” – bombarded by molecules Robert Brown, 1827 oSee next slides, or http://www.is.wayne.edu/drbowen/Class-Room_Models/Welcome.htm http://www.colorado.edu/physics/phet/web-pages/simulations-base.html http://www.is.wayne.edu/drbowen/Class-Room_Models/Welcome.htm http://www.colorado.edu/physics/phet/web-pages/simulations-base.html oNow we have more direct evidence

29. 11/24/08Atoms and Stars, Class 1229Atoms and Stars, Class 1229 Brownian Motion (Review) Jagged tracks of pollen particles. Gas molecules mode visible. Jagged tracks explained as due to collisions with gas molecules.

30. Expanding Circles Implication #1, Example 3

31. 11/24/08Atoms and Stars, Class 1231Atoms and Stars, Class 1231 Expanding Circles (Q16) Review: science started out as isolated areas Then areas expand – science always pushing its boundaries Implication #1: What happens when two expanding circles meet? Implication #2: What happens when circles fill the space? oMy answer: science drives technology (see C8S15-19 for details)

32. 11/24/08Atoms and Stars, Class 1232Atoms and Stars, Class 1232 Expanding Circles Implication #1: What happens when two expanding circles meet? I promised three examples (Q15) 1.Newton uniting celestial (stars) and terrestrial (on land) – already done (C12S12) 2.James Clerk Maxwell uniting Electricity and Magnetism (Class 9, November 3) 3.Ludwig Boltzmann uniting atoms and Newton’s Laws (this class)

33. 11/24/08Atoms and Stars, Class 1233Atoms and Stars, Class 1233 Expanding Circles (Q15) Example 3: Statistical Mechanics Ludwig Boltzmann, end of 19th century oPhysicists had never accepted idea of atoms oBoltzmann (Austrian physicist) one of first oWorked out Newtonian mechanics for a gas of colliding atoms and molecules - Statistical Mechanics With J. Willard Gibbs – now has his own stamp oDB: “Atomic Theory meets Isaac Newton” oSame results as Thermodynamics (accepted, see later) Also explained how those results came about (explanatory) Other physicists still sharply rejected these ideas oMay have contributed to Boltzmann's 1906 suicide

34. 11/24/08Atoms and Stars, Class 1234Atoms and Stars, Class 1234 Expanding Circles Now Boltzmann honored as pioneer oStatistical Mechanics very important Significantly modified by Quantum Mechanics. Second Law of Thermodynamics oIf a hot object and a cold one are in contact, energy always goes from hot to cold Atoms in hot object more energetic (Rumford), travel more Slowed down by collisions with slower atoms from cold object, but these are sped up Statistical Mechanics explains why this happens Demonstration – diffusion – atoms of dye

35. 11/24/08Atoms and Stars, Class 1235Atoms and Stars, Class 1235 Expanding Circles Statistical Mechanics Theory: molecules in a gas move and collide randomly, governed by laws of statistics and by Newton’s Laws oToo many particles to follow each, so calculate the averages Once particles mix, essentially no chance of their separating again Computer simulation of this mixingComputer simulation

36. 11/24/08Atoms and Stars, Class 1236Atoms and Stars, Class 1236 A Taste of Statistical Mechanics See next slide, but here is the explanation o“Gas” with spaces for 4 atoms oGas divided into left & right halves oTwo green atoms, two blue oIn each half, the 4 atoms arrange randomly oAtoms too small to see, we see the average color in each half oOne chance for left being green, right blue oAnother chance for the opposite o4 chances for mixed – turquoise Chances get more lopsided with more atoms

37. 11/24/08Atoms and Stars, Class 1237Atoms and Stars, Class 1237 A Taste of Statistical Mechanics Start with gas (4 slots) and atoms We see average of color in each half Most common is mixed Odds more lopsided with more atoms

38. Two Different Types of Things Background for reading for 12/8, “Knowledge or Certainty “

39. 11/24/08Atoms and Stars, Class 1239Atoms and Stars, Class 1239 Two different types of things Particle (“thing,” “object”) oExamples: baseball, soup can, projectile, star oOne location (or center) oNewton’s three laws govern motion Wave oExamples: waves in water, sound waves, radio waves oSpread out, exists in many places o“Wave Equations” governed motion (not Newton)

40. 11/24/08Atoms and Stars, Class 1240Atoms and Stars, Class 1240 Two different types of things ParticleWave Position:Definite – one position (center) Spread out, no one place Try to catch it – result is: Get all or noneOnly get part, if that Collision with another: Ricochet, bounce, shatter Pass through each other Existence:All by itselfIn something – the “medium” (before Maxwell)

41. 11/24/08Atoms and Stars, Class 1241Atoms and Stars, Class 1241 Demonstrations PhET (Physics Education Technology) http://phet.colorado.edu/simulations/sims.php?sim=Gas_Properties http://phet.colorado.edu/simulations/sims.php?sim=Gas_Properties oParticles: Gas Properties – they bounce oWaves: Sound >> Interference by Reflection Interference: light  peak, dark  trough ohttp://www.colorado.edu/physics/2000/schroedinger/big_interference.html – some areas gray (unlit)http://www.colorado.edu/physics/2000/schroedinger/big_interference.html Light: early 1800s, Thomas Young proved light is a wave – “double slit experiment” ohttp://www.colorado.edu/physics/2000/schroedinger/two-slit2.htmlhttp://www.colorado.edu/physics/2000/schroedinger/two-slit2.html oConfine a wave – it spreads out

42. 11/24/08Atoms and Stars, Class 1242Atoms and Stars, Class 1242 Particles collide… Particles of gas mix together, collide

43. 11/24/08Atoms and Stars, Class 1243Atoms and Stars, Class 1243 but waves pass through each otherwaves pass through each other Sound wave and its reflection (type – sound - is unimportant here)

44. 11/24/08Atoms and Stars, Class 1244Atoms and Stars, Class 1244 Waves “interfering” Confine a wave and it spreads out

45. 11/24/08Atoms and Stars, Class 1245Atoms and Stars, Class 1245 Waves Wavelength – distance between peaks (or troughs) Fixed speed Until 20 th century, Wave / Particle – we thought everything was one or the other Wavelength

46. 11/24/08Atoms and Stars, Class 1246Atoms and Stars, Class 1246 Wave-Particle Duality In 20 th century, with rise of Quantum Mechanics, we understood that everything was both. oFor a wave, x (position) and v (velocity) connected – see later slide oLed to “Uncertainty Principle” Irreducible uncertainty in our knowledge

47. 11/24/08Atoms and Stars, Class 1247Atoms and Stars, Class 1247 Uncertainty Principle 1795 Carl Friedrich Gauss (college student) Uncertainty called  (“sigma”, LC Greek s) Also Uncertainty Principal 1927 Werner Heisenberg – cannot locate particle exactly

48. 11/24/08Atoms and Stars, Class 1248Atoms and Stars, Class 1248 Uncertainty Principle No practical effect at macroscopic level oA philosophical problem with The Mechanical Universe and with “The God’s eye view” or The Clockwork Universe over age of universe Important at atomic and molecular level oUncertainties are large on atomic scale oWhat underlies our reality is strange

49. 11/24/08Atoms and Stars, Class 1249Atoms and Stars, Class 1249 Uncertainty Principle Example: A = 20 / C Uncertainty small for large masses, large for small masses, atoms have very small masses CA 210Divide by small number, get big number. Divide by larger number, get smaller number. 54

50. Experiment 9

51. 11/24/08Atoms and Stars, Class 1251Atoms and Stars, Class 1251 Experiment 9: overall Important conclusions from Part 1 (Circle): oThe formula is almost certainly correct oValue of  almost certainly correct oThe method for measuring C is valid within.1” or.2” Method: putting pins along path, looping string along pins, removing string and measuring its length Circle part and ellipse part are connected. DO NOT treat them as separate. Should measurement errors be the same, or different? If they are different, how can this happen?

52. Experiment 7 Specific Gravity

53. 11/24/08Atoms and Stars, Class 1253 Experiment 7 Checking on Archimedes: saw water rise when he got into bathtub, ran through city shouting “Eureka” Displaced water – submerse object in water, water level rises, this is displaced water = volume of object Specific Gravity – property of material: SG: (object’s weight)/(displaced water’s weight) S.G. is a help in identifying the material Weighing objects (wood block, dumbbell, displaced water): oWeight in pounds and ounces using fish scale oUse string slings for block and dumbbell

54. 11/24/08Atoms and Stars, Class 1254 Experiment 7 Using the fish scales: oTurn on oWait for numbers to stop flashing While numbers are flashing, scale is adjusting the zero Will show 0 0 when flashing stops oAfter numbers have stopped flashing, THEN attach weight and read it Reading is pounds and ounces Convert ounces to decimal pounds by dividing by 16

55. 11/24/08Atoms and Stars, Class 1255 Experiment 7 (cont’d) Converting pounds and ounces to decimal pounds: 1.Divide # ounces by 16 (result between 0 and 1), call this “X” (round to nearest tenth) 2.Check: multiply X by 16, should get about the original # ounces – SHOW THIS CHECK ON DATA SHEET !!! 3.Add X to # pounds to get decimal pounds

56. 11/24/08Atoms and Stars, Class 1256 Experiment 7 (cont’d) Converting inches and sixteenths to decimal inches: oSame as for pounds and ounces to decimal ounces, INCLUDING CHECK !!! (previous Slide) For step # 5, ignore rounded edges and grooves in block: V = L × W × H Same for #6, volume of water oH = change in height with/without block

57. 11/24/08Atoms and Stars, Class 1257 Experiment 7 (cont’d) For both wood block and dumbbell: oFind object’s weight and weight of displaced water, divide to find Specific Gravity For wood block only: oFind object’s volume and compare to volume of displaced water. Archimedes: volumes the same For dumbbell only: oFind object’s weight “in water,” compare with weight “in air” (normal) and weight of displaced water

58. 11/24/08Atoms and Stars, Class 1258 Experiment 7 (cont’d) For #7, you will probably have to use different amounts of water in the tub for each object. oHold object down if necessary (i.e. wood), cover with water, remove object, then start that part of the lab

59. 11/24/08Atoms and Stars, Class 1259 Experiment 7 (cont’d) Measuring length starting from 1” can be more accurate, but be careful oSubtract the 1 from the end reading oWhat is the distance between two marks below? 1½” or 2½”?